FTM Based Secure Ranging Error Recovery

ABSTRACT

Methods for performing error recovery during a ranging procedure may include negotiation one or more ranging parameters, including a set of secure training sequences and receipt of a first ranging frame that may include a first dialog token and may have an appended first secure training sequence. The first ranging frame may be decoded based on the first dialog token but not correlated based on the first secure training sequence. A first acknowledgment that may include an appended second secure training sequence may be transmitted. The second secure training sequence may be associated with a prior dialog token. A second ranging frame that may include a second dialog token and may have an appended third secure training sequence may be received. The second ranging frame may be decoded based on the third dialog token and correlated based on the third secure training sequence.

PRIORITY DATA

This application claims benefit of priority to U.S. ProvisionalApplication Ser. No. 62/728,918, titled “FTM Based Secure Ranging ErrorRecovery”, filed Sep. 10, 2018, by Su Khiong Yong, Christiaan A.Hartman, Jarkko L. Kneckt, Mingguang Xu, Mithat C. Dogan, and Yong Liu,which is hereby incorporated by reference in its entirety as thoughfully and completely set forth herein.

FIELD

The present application relates to wireless communications, includingtechniques for wireless communication among wireless stations in awireless networking system, including error recovery during secureranging based on fine timing measurements.

DESCRIPTION OF THE RELATED ART

Wireless communication systems are rapidly growing in usage. Further,wireless communication technology has evolved from voice-onlycommunications to also include the transmission of data, such asInternet and multimedia content. A popular short/intermediate rangewireless communication standard is wireless local area network (WLAN).Most modern WLANs are based on the IEEE 802.11 standard (or 802.11, forshort) and are marketed under the Wi-Fi brand name. WLAN networks linkone or more devices to a wireless access point, which in turn providesconnectivity to the wider area Internet.

In 802.11 systems, devices that wirelessly connect to each other arereferred to as “stations”, “mobile stations”, “user devices” or STA orUE for short. Wireless stations can be either wireless access points orwireless clients (or mobile stations). Access points (APs), which arealso referred to as wireless routers, act as base stations for thewireless network. APs transmit and receive radio frequency signals forcommunication with wireless client devices. APs can also typicallycouple to the Internet in a wired fashion. Wireless clients operating onan 802.11 network can be any of various devices such as laptops, tabletdevices, smart phones, or fixed devices such as desktop computers.Wireless client devices are referred to herein as user equipment (or UEfor short). Some wireless client devices are also collectively referredto herein as mobile devices or mobile stations (although, as notedabove, wireless client devices overall may be stationary devices aswell).

Mobile electronic devices may take the form of smart phones or tabletsthat a user typically carries. Wearable devices (also referred to asaccessory devices) are a newer form of mobile electronic device, oneexample being smart watches. Additionally, low-cost low-complexitywireless devices intended for stationary or nomadic deployment are alsoproliferating as part of the developing “Internet of Things”. In otherwords, there is an increasingly wide range of desired devicecomplexities, capabilities, traffic patterns, and other characteristics.

One use case for wireless communication includes ranging communication.Ranging can provide the distance between one wireless device and another(e.g., the distance between wireless nodes and/or wireless stations).However, in existing wireless communication technologies rangingsensitivity may be bounded by data decode sensitivity. Accordingly,improvements in the field are desired.

SUMMARY

Embodiments described herein relate to error recovery during secureranging between wireless devices.

Embodiments relate to a wireless station that includes one or moreantennas, one or more radios, and one or more processors coupled(directly or indirectly) to the radios. At least one radio is configuredto perform Wi-Fi communications. The wireless station may perform voiceand/or data communications, as well as the methods described herein.

In some embodiments, a wireless device may be configured to negotiateone or more ranging parameters that may include at least a set of securetraining sequences. In addition, the wireless device may receive a firstranging frame that may include a first dialog token. A first securetraining sequence of the set of secure training sequences may appendedto the first ranging frame. The wireless device may determine that thefirst ranging frame can be decoded based on the first dialog token butnot correlated based on the first secure training sequence. The wirelessdevice may transmit a first acknowledgment. A second secure trainingsequence of the set of secure training sequences may be appended to thefirst acknowledgment and the second secure training sequence may beassociated with a prior dialog token. The wireless device may receive asecond ranging frame that may include a second dialog token. A thirdsecure training sequence of the set of secure training sequences may beappended to the second ranging frame. The wireless device may determinethat the second ranging frame can be decoded based on the third dialogtoken and correlated based on the third secure training sequence.

In some embodiments, a wireless device may negotiate one or more rangingparameters that may include at least a set of secure training sequencesand may transmit a first ranging frame that may include a first dialogtoken. A first secure training sequence of the set of secure trainingsequences may be appended to the first ranging frame. The wirelessdevice may transmit a second ranging frame that may include a seconddialog token. A second secure training sequence of the set of securetraining sequences may be appended to the second ranging frame. Thewireless device may receive a first acknowledgment. A third securetraining sequence of the set of secure training sequences may beappended to the first acknowledgment and the third secure trainingsequence may be associated with the first dialog token. The wirelessdevice may determine that the first acknowledgment can be decoded butcannot be correlated based on the third secure training sequence and maytransmit a third ranging frame that may include a third dialog token. Afourth secure training sequence of the set of secure training sequencesmay be appended to the third ranging frame.

This Summary is intended to provide a brief overview of some of thesubject matter described in this document. Accordingly, it will beappreciated that the above-described features are merely examples andshould not be construed to narrow the scope or spirit of the subjectmatter described herein in any way. Other features, aspects, andadvantages of the subject matter described herein will become apparentfrom the following Detailed Description, Figures, and Claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present subject matter can be obtainedwhen the following detailed description of the embodiments is consideredin conjunction with the following drawings.

FIG. 1A illustrates an example wireless communication system, accordingto some embodiments.

FIG. 1B illustrates an example simplified block diagram of a wirelessdevice, according to some embodiments.

FIG. 1C illustrates an example WLAN communication system, according tosome embodiments.

FIG. 2 illustrates an example simplified block diagram of a WLAN AccessPoint (AP), according to some embodiments.

FIG. 3A illustrates an example simplified block diagram of a wirelessstation (UE), according to some embodiments.

FIG. 3B illustrates an example simplified block diagram of a wirelessnode, according to some embodiments.

FIG. 4A illustrates a diagram of an example of signaling for a rangingprocedure.

FIG. 4B illustrates a diagram of an example of signaling for a securedranging procedure.

FIGS. 4C-4D illustrate diagrams of examples of signaling during failureof a secured ranging procedure.

FIG. 5A illustrates an example of a timeline and frame exchange betweenan initiating station and a responding station, according to someembodiments.

FIGS. 5B-5C illustrate various examples of error recovery for an FTMbased secure ranging procedure, according to some embodiments.

FIG. 6 illustrates a block diagram of an example of a method for errorrecovery for an FTM based secure ranging procedure, according to someembodiments.

FIG. 7 illustrates a block diagram of another example of a method forerror recovery for an FTM based secure ranging procedure, according tosome embodiments.

While the features described herein are susceptible to variousmodifications and alternative forms, specific embodiments thereof areshown by way of example in the drawings and are herein described indetail. It should be understood, however, that the drawings and detaileddescription thereto are not intended to be limiting to the particularform disclosed, but on the contrary, the intention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the subject matter as defined by the appended claims.

DETAILED DESCRIPTION Acronyms

Various acronyms are used throughout the present application.Definitions of the most prominently used acronyms that may appearthroughout the present application are provided below:

UE: User Equipment

AP: Access Point

TX: Transmission/Transmit

RX: Reception/Receive

LAN: Local Area Network

WLAN: Wireless LAN

RAT: Radio Access Technology

TTL: time to live

SU: Single user

MU: Multi user

NDP: Null Data Packet

NDPA: NDP Announcement

VHT: 802.11 very high throughput

VHTz: NDP sounding-based 802.11az SU protocol

iSTA: Initiating station of a ranging procedure

rSTA: Responding station of a ranging procedure

ToA: time of arrival of a packet

ToD: time of departure of a packet

LMR: location measurement report

SIFS: short interframe space

FTM: fine timing measurement

Terminology

The following is a glossary of terms used in this disclosure:

Memory Medium—Any of various types of non-transitory memory devices orstorage devices. The term “memory medium” is intended to include aninstallation medium, e.g., a CD-ROM, floppy disks, or tape device; acomputer system memory or random-access memory such as DRAM, DDR RAM,SRAM, EDO RAM, Rambus RAM, etc.; a non-volatile memory such as a Flash,magnetic media, e.g., a hard drive, or optical storage; registers, orother similar types of memory elements, etc. The memory medium mayinclude other types of non-transitory memory as well or combinationsthereof. In addition, the memory medium may be located in a firstcomputer system in which the programs are executed, or may be located ina second different computer system which connects to the first computersystem over a network, such as the Internet. In the latter instance, thesecond computer system may provide program instructions to the firstcomputer for execution. The term “memory medium” may include two or morememory mediums which may reside in different locations, e.g., indifferent computer systems that are connected over a network. The memorymedium may store program instructions (e.g., embodied as computerprograms) that may be executed by one or more processors.

Carrier Medium—a memory medium as described above, as well as a physicaltransmission medium, such as a bus, network, and/or other physicaltransmission medium that conveys signals such as electrical,electromagnetic, or digital signals.

Computer System—any of various types of computing or processing systems,including a personal computer system (PC), mainframe computer system,workstation, network appliance, Internet appliance, personal digitalassistant (PDA), television system, grid computing system, or otherdevice or combinations of devices. In general, the term “computersystem” can be broadly defined to encompass any device (or combinationof devices) having at least one processor that executes instructionsfrom a memory medium.

Mobile Device (or Mobile Station)—any of various types of computersystems devices which are mobile or portable and which performs wirelesscommunications using WLAN communication. Examples of mobile devicesinclude mobile telephones or smart phones (e.g., iPhone™, Android™-basedphones), and tablet computers such as iPad™ Samsung Galaxy™, etc.Various other types of devices would fall into this category if theyinclude Wi-Fi or both cellular and Wi-Fi communication capabilities,such as laptop computers (e.g., MacBook™), portable gaming devices(e.g., Nintendo DS™, PlayStation Portable™, Gameboy Advance™, iPhone™),portable Internet devices, and other handheld devices, as well aswearable devices such as smart watches, smart glasses, headphones,pendants, earpieces, etc. In general, the term “mobile device” can bebroadly defined to encompass any electronic, computing, and/ortelecommunications device (or combination of devices) which is easilytransported by a user and capable of wireless communication using WLANor Wi-Fi.

Wireless Device (or Wireless Station)—any of various types of computersystems devices which performs wireless communications using WLANcommunications. As used herein, the term “wireless device” may refer toa mobile device, as defined above, or to a stationary device, such as astationary wireless client or a wireless base station. For example, awireless device may be any type of wireless station of an 802.11 system,such as an access point (AP) or a client station (STA or UE). Furtherexamples include televisions, media players (e.g., AppleTV™, Roku™,Amazon FireTV™, Google Chromecast™, etc.), refrigerators, laundrymachines, thermostats, and so forth.

WLAN—The term “WLAN” has the full breadth of its ordinary meaning, andat least includes a wireless communication network or RAT that isserviced by WLAN access points and which provides connectivity throughthese access points to the Internet. Most modern WLANs are based on IEEE802.11 standards and are marketed under the name “Wi-Fi”. A WLAN networkis different from a cellular network.

Processing Element—refers to various implementations of digitalcircuitry that perform a function in a computer system. Additionally,processing element may refer to various implementations of analog ormixed-signal (combination of analog and digital) circuitry that performa function (or functions) in a computer or computer system. Processingelements include, for example, circuits such as an integrated circuit(IC), ASIC (Application Specific Integrated Circuit), portions orcircuits of individual processor cores, entire processor cores,individual processors, programmable hardware devices such as a fieldprogrammable gate array (FPGA), and/or larger portions of systems thatinclude multiple processors.

Automatically—refers to an action or operation performed by a computersystem (e.g., software executed by the computer system) or device (e.g.,circuitry, programmable hardware elements, ASICs, etc.), without userinput directly specifying or performing the action or operation. Thus,the term “automatically” is in contrast to an operation being manuallyperformed or specified by the user, where the user provides input todirectly perform the operation. An automatic procedure may be initiatedby input provided by the user, but the subsequent actions that areperformed “automatically” are not specified by the user, e.g., are notperformed “manually”, where the user specifies each action to perform.For example, a user filling out an electronic form by selecting eachfield and providing input specifying information (e.g., by typinginformation, selecting check boxes, radio selections, etc.) is fillingout the form manually, even though the computer system must update theform in response to the user actions. The form may be automaticallyfilled out by the computer system where the computer system (e.g.,software executing on the computer system) analyzes the fields of theform and fills in the form without any user input specifying the answersto the fields. As indicated above, the user may invoke the automaticfilling of the form, but is not involved in the actual filling of theform (e.g., the user is not manually specifying answers to fields butrather they are being automatically completed). The presentspecification provides various examples of operations beingautomatically performed in response to actions the user has taken.

Concurrent—refers to parallel execution or performance, where tasks,processes, signaling, messaging, or programs are performed in an atleast partially overlapping manner. For example, concurrency may beimplemented using “strong” or strict parallelism, where tasks areperformed (at least partially) in parallel on respective computationalelements, or using “weak parallelism”, where the tasks are performed inan interleaved manner, e.g., by time multiplexing of execution threads.

Configured to—Various components may be described as “configured to”perform a task or tasks. In such contexts, “configured to” is a broadrecitation generally meaning “having structure that” performs the taskor tasks during operation. As such, the component can be configured toperform the task even when the component is not currently performingthat task (e.g., a set of electrical conductors may be configured toelectrically connect a module to another module, even when the twomodules are not connected). In some contexts, “configured to” may be abroad recitation of structure generally meaning “having circuitry that”performs the task or tasks during operation. As such, the component canbe configured to perform the task even when the component is notcurrently on. In general, the circuitry that forms the structurecorresponding to “configured to” may include hardware circuits.

Various components may be described as performing a task or tasks, forconvenience in the description. Such descriptions should be interpretedas including the phrase “configured to.” Reciting a component that isconfigured to perform one or more tasks is expressly intended not toinvoke 35 U.S.C. § 112(f) interpretation for that component.

FIGS. 1A-1B—Wireless Communication System

FIG. 1A illustrates an exemplary (and simplified) wireless communicationsystem in which aspects of this disclosure may be implemented. It isnoted that the system of FIG. 1A is merely one example of a possiblesystem, and embodiments of this disclosure may be implemented in any ofvarious systems, as desired.

As shown, the exemplary wireless communication system includes a(“first”) wireless device 102 in communication with another (“second”)wireless device. The first wireless device 102 and the second wirelessdevice 104 may communicate wirelessly using any of a variety of wirelesscommunication techniques, potentially including ranging wirelesscommunication techniques.

As one possibility, the first wireless device 102 and the secondwireless device 104 may perform ranging using wireless local areanetworking (WLAN) communication technology (e.g., IEEE 802.11/Wi-Fibased communication) and/or techniques based on WLAN wirelesscommunication. One or both of the wireless device 102 and the wirelessdevice 104 may also be capable of communicating via one or moreadditional wireless communication protocols, such as any of Bluetooth(BT), Bluetooth Low Energy (BLE), near field communication (NFC), GSM,UMTS (WCDMA, TDSCDMA), LTE, LTE-Advanced (LTE-A), NR, 3GPP2 CDMA2000(e.g., 1×RTT, 1×EV-DO, HRPD, eHRPD), Wi-MAX, GPS, etc.

The wireless devices 102 and 104 may be any of a variety of types ofwireless device. As one possibility, one or more of the wireless devices102 and/or 104 may be a substantially portable wireless user equipment(UE) device, such as a smart phone, handheld device, a wearable devicesuch as a smart watch, a tablet, a motor vehicle, or virtually any typeof wireless device. As another possibility, one or more of the wirelessdevices 102 and/or 104 may be a substantially stationary device, such asa set top box, media player (e.g., an audio or audiovisual device),gaming console, desktop computer, appliance, door, access point, basestation, or any of a variety of other types of device.

Each of the wireless devices 102 and 104 may include wirelesscommunication circuitry configured to facilitate the performance ofwireless communication, which may include various digital and/or analogradio frequency (RF) components, a processor that is configured toexecute program instructions stored in memory, a programmable hardwareelement such as a field-programmable gate array (FPGA), and/or any ofvarious other components. The wireless device 102 and/or the wirelessdevice 104 may perform any of the method embodiments described herein,or any portion of any of the method embodiments described herein, usingany or all of such components.

Each of the wireless devices 102 and 104 may include one or moreantennas for communicating using one or more wireless communicationprotocols. In some cases, one or more parts of a receive and/or transmitchain may be shared between multiple wireless communication standards;for example, a device might be configured to communicate using either ofBluetooth or Wi-Fi using partially or entirely shared wirelesscommunication circuitry (e.g., using a shared radio or at least sharedradio components). The shared communication circuitry may include asingle antenna, or may include multiple antennas (e.g., for MIMO) forperforming wireless communications. Alternatively, a device may includeseparate transmit and/or receive chains (e.g., including separateantennas and other radio components) for each wireless communicationprotocol with which it is configured to communicate. As a furtherpossibility, a device may include one or more radios or radio componentswhich are shared between multiple wireless communication protocols, andone or more radios or radio components which are used exclusively by asingle wireless communication protocol. For example, a device mightinclude a shared radio for communicating using one or more of LTE,CDMA2000 1×RTT, GSM, and/or 5G NR, and separate radios for communicatingusing each of Wi-Fi and Bluetooth. Other configurations are alsopossible.

As previously noted, aspects of this disclosure may be implemented inconjunction with the wireless communication system of FIG. 1A. Forexample, a wireless device (e.g., either of wireless devices 102 or 104)may perform error recovery for a ranging procedure. Thus, in someembodiments, the wireless device may be configured to negotiate one ormore ranging parameters that may include at least a set of securetraining sequences. In addition, the wireless device may receive a firstranging frame that may include a first dialog token. A first securetraining sequence of the set of secure training sequences may appendedto the first ranging frame. The wireless device may determine that thefirst ranging frame can be decoded based on the first dialog token butnot correlated based on the first secure training sequence. The wirelessdevice may transmit a first acknowledgment. A second secure trainingsequence of the set of secure training sequences may be appended to thefirst acknowledgment and the second secure training sequence may beassociated with a prior dialog token. The wireless device may receive asecond ranging frame that may include a second dialog token. A thirdsecure training sequence of the set of secure training sequences may beappended to the second ranging frame. The wireless device may determinethat the second ranging frame can be decoded based on the third dialogtoken and correlated based on the third secure training sequence.

In some embodiments, a wireless device may negotiate one or more rangingparameters that may include at least a set of secure training sequencesand may transmit a first ranging frame that may include a first dialogtoken. A first secure training sequence of the set of secure trainingsequences may be appended to the first ranging frame. The wirelessdevice may transmit a second ranging frame that may include a seconddialog token. A second secure training sequence of the set of securetraining sequences may be appended to the second ranging frame. Thewireless device may receive a first acknowledgment. A third securetraining sequence of the set of secure training sequences may beappended to the first acknowledgment and the third secure trainingsequence may be associated with the first dialog token. The wirelessdevice may determine that the first acknowledgment can be decoded butcannot be correlated based on the third secure training sequence and maytransmit a third ranging frame that may include a third dialog token. Afourth secure training sequence of the set of secure training sequencesmay be appended to the third ranging frame.

FIG. 1B illustrates an exemplary wireless device 100 (e.g.,corresponding to wireless devices 102 and/or 104) that may be configuredfor use in conjunction with various aspects of the present disclosure.The device 100 may be any of a variety of types of device and may beconfigured to perform any of a variety of types of functionality. Thedevice 100 may be a substantially portable device or may be asubstantially stationary device, potentially including any of a varietyof types of device. The device 100 may be configured to perform one ormore ranging wireless communication techniques or features, such as anyof the techniques or features illustrated and/or described subsequentlyherein with respect to any or all of the Figures.

As shown, the device 100 may include a processing element 10. Theprocessing element may include or be coupled to one or more memoryelements. For example, the device 100 may include one or more memorymedia (e.g., memory 105), which may include any of a variety of types ofmemory and may serve any of a variety of functions. For example, memory105 could be RAM serving as a system memory for processing element 101.Other types and functions are also possible.

Additionally, the device 100 may include wireless communicationcircuitry 130. The wireless communication circuitry may include any of avariety of communication elements (e.g., antenna for wirelesscommunication, analog and/or digital communicationcircuitry/controllers, etc.) and may enable the device to wirelesslycommunicate using one or more wireless communication protocols.

Note that in some cases, the wireless communication circuitry 130 mayinclude its own processing element (e.g., a baseband processor), e.g.,in addition to the processing element 101. For example, the processingelement 101 may be an ‘application processor’ whose primary function maybe to support application layer operations in the device 100, while thewireless communication circuitry 130 may be a ‘baseband processor’ whoseprimary function may be to support baseband layer operations (e.g., tofacilitate wireless communication between the device 100 and otherdevices) in the device 100. In other words, in some cases the device 100may include multiple processing elements (e.g., may be a multi-processordevice). Other configurations (e.g., instead of or in addition to anapplication processor/baseband processor configuration) utilizing amulti-processor architecture are also possible.

The device 100 may additionally include any of a variety of othercomponents (not shown) for implementing device functionality, dependingon the intended functionality of the device 100, which may includefurther processing and/or memory elements (e.g., audio processingcircuitry), one or more power supply elements (which may rely on batterypower and/or an external power source) user interface elements (e.g.,display, speaker, microphone, camera, keyboard, mouse, touchscreen,etc.), and/or any of various other components.

The components of the device 100, such as processing element 101, memory105, and wireless communication circuitry 130, may be operativelycoupled via one or more interconnection interfaces, which may includeany of a variety of types of interface, possibly including a combinationof multiple types of interface. As one example, a USB high-speedinter-chip (HSIC) interface may be provided for inter-chipcommunications between processing elements. Alternatively (or inaddition), a universal asynchronous receiver transmitter (UART)interface, a serial peripheral interface (SPI), inter-integrated circuit(I2C), system management bus (SMBus), and/or any of a variety of othercommunication interfaces may be used for communications between variousdevice components. Other types of interfaces (e.g., intra-chipinterfaces for communication within processing element 101, peripheralinterfaces for communication with peripheral components within orexternal to device 100, etc.) may also be provided as part of device100.

FIG. 1C—WLAN System

FIG. 1C illustrates an example WLAN system according to someembodiments. As shown, the exemplary WLAN system includes a plurality ofwireless client stations or devices, or user equipment (UEs), 106 thatare configured to communicate over a wireless communication channel 142with an Access Point (AP) 112. The AP 112 may be a Wi-Fi access point.The AP 112 may communicate via a wired and/or a wireless communicationchannel 150 with one or more other electronic devices (not shown) and/oranother network 152, such as the Internet. Additional electronicdevices, such as the remote device 154, may communicate with componentsof the WLAN system via the network 152. For example, the remote device154 may be another wireless client station. The WLAN system may beconfigured to operate according to any of various communicationsstandards, such as the various IEEE 802.11 standards. In someembodiments, at least one wireless device 106 is configured tocommunicate directly with one or more neighboring mobile devices,without use of the access point 112.

Further, in some embodiments, as further described below, a wirelessdevice 106 (which may be an exemplary implementation of device 100) maybe configured to perform error recovery for a ranging procedure. Thus,in some embodiments, the wireless device 106 may be configured tonegotiate one or more ranging parameters that may include at least a setof secure training sequences. In addition, the wireless device 106 mayreceive a first ranging frame that may include a first dialog token. Afirst secure training sequence of the set of secure training sequencesmay appended to the first ranging frame. The wireless device 106 maydetermine that the first ranging frame can be decoded based on the firstdialog token but not correlated based on the first secure trainingsequence. The wireless device 106 may transmit a first acknowledgment. Asecond secure training sequence of the set of secure training sequencesmay be appended to the first acknowledgment and the second securetraining sequence may be associated with a prior dialog token. Thewireless device 106 may receive a second ranging frame that may includea second dialog token. A third secure training sequence of the set ofsecure training sequences may be appended to the second ranging frame.The wireless device 106 may determine that the second ranging frame canbe decoded based on the third dialog token and correlated based on thethird secure training sequence.

In some embodiments, a wireless device 106 may negotiate one or moreranging parameters that may include at least a set of secure trainingsequences and may transmit a first ranging frame that may include afirst dialog token. A first secure training sequence of the set ofsecure training sequences may be appended to the first ranging frame.The wireless device 106 may transmit a second ranging frame that mayinclude a second dialog token. A second secure training sequence of theset of secure training sequences may be appended to the second rangingframe. The wireless device 106 may receive a first acknowledgment. Athird secure training sequence of the set of secure training sequencesmay be appended to the first acknowledgment and the third securetraining sequence may be associated with the first dialog token. Thewireless device 106 may determine that the first acknowledgment can bedecoded but cannot be correlated based on the third secure trainingsequence and may transmit a third ranging frame that may include a thirddialog token. A fourth secure training sequence of the set of securetraining sequences may be appended to the third ranging frame.

FIG. 2—Access Point Block Diagram

FIG. 2 illustrates an exemplary block diagram of an access point (AP)112, which may be one possible exemplary implementation of the device100 illustrated in FIG. 1B. It is noted that the block diagram of the APof FIG. 2 is only one example of a possible system. As shown, the AP 112may include processor(s) 204 which may execute program instructions forthe AP 112. The processor(s) 204 may also be coupled (directly orindirectly) to memory management unit (MMU) 240, which may be configuredto receive addresses from the processor(s) 204 and to translate thoseaddresses to locations in memory (e.g., memory 260 and read only memory(ROM) 250) or to other circuits or devices.

The AP 112 may include at least one network port 270. The network port270 may be configured to couple to a wired network and provide aplurality of devices, such as mobile devices 106, access to theInternet. For example, the network port 270 (or an additional networkport) may be configured to couple to a local network, such as a homenetwork or an enterprise network. For example, port 270 may be anEthernet port. The local network may provide connectivity to additionalnetworks, such as the Internet.

The AP 112 may include at least one antenna 234, which may be configuredto operate as a wireless transceiver and may be further configured tocommunicate with mobile device 106 via wireless communication circuitry230. The antenna 234 communicates with the wireless communicationcircuitry 230 via communication chain 232. Communication chain 232 mayinclude one or more receive chains, one or more transmit chains or both.The wireless communication circuitry 230 may be configured tocommunicate via Wi-Fi or WLAN, e.g., 802.11. The wireless communicationcircuitry 230 may also, or alternatively, be configured to communicatevia various other wireless communication technologies, including, butnot limited to, Long-Term Evolution (LTE), LTE Advanced (LTE-A), GlobalSystem for Mobile (GSM), Wideband Code Division Multiple Access (WCDMA),CDMA2000, etc., for example when the AP is co-located with a basestation in case of a small cell, or in other instances when it may bedesirable for the AP 112 to communicate via various different wirelesscommunication technologies.

Further, in some embodiments, as further described below, AP 112 may beconfigured to perform error recovery for a ranging procedure. Thus, insome embodiments, the AP 112 may be configured to negotiate one or moreranging parameters that may include at least a set of secure trainingsequences. In addition, the AP 112 may receive a first ranging framethat may include a first dialog token. A first secure training sequenceof the set of secure training sequences may appended to the firstranging frame. The AP 112 may determine that the first ranging frame canbe decoded based on the first dialog token but not correlated based onthe first secure training sequence. The AP 112 may transmit a firstacknowledgment. A second secure training sequence of the set of securetraining sequences may be appended to the first acknowledgment and thesecond secure training sequence may be associated with a prior dialogtoken. The AP 112 may receive a second ranging frame that may include asecond dialog token. A third secure training sequence of the set ofsecure training sequences may be appended to the second ranging frame.The AP 112 may determine that the second ranging frame can be decodedbased on the third dialog token and correlated based on the third securetraining sequence.

In some embodiments, an AP 112 may negotiate one or more rangingparameters that may include at least a set of secure training sequencesand may transmit a first ranging frame that may include a first dialogtoken. A first secure training sequence of the set of secure trainingsequences may be appended to the first ranging frame. The AP 112 maytransmit a second ranging frame that may include a second dialog token.A second secure training sequence of the set of secure trainingsequences may be appended to the second ranging frame. The AP 112 mayreceive a first acknowledgment. A third secure training sequence of theset of secure training sequences may be appended to the firstacknowledgment and the third secure training sequence may be associatedwith the first dialog token. The AP 112 may determine that the firstacknowledgment can be decoded but cannot be correlated based on thethird secure training sequence and may transmit a third ranging framethat may include a third dialog token. A fourth secure training sequenceof the set of secure training sequences may be appended to the thirdranging frame.

FIG. 3A—Client Station Block Diagram

FIG. 3A illustrates an example simplified block diagram of a clientstation 106, which may be one possible exemplary implementation of thedevice 100 illustrated in FIG. 1B. According to embodiments, clientstation 106 may be a user equipment (UE) device, a mobile device ormobile station, and/or a wireless device or wireless station. As shown,the client station 106 may include a system on chip (SOC) 300, which mayinclude portions for various purposes. The SOC 300 may be coupled tovarious other circuits of the client station 106. For example, theclient station 106 may include various types of memory (e.g., includingNAND flash 310), a connector interface (I/F) (or dock) 320 (e.g., forcoupling to a computer system, dock, charging station, etc.), thedisplay 360, cellular communication circuitry 330 such as for LTE, GSM,etc., and short to medium range wireless communication circuitry 329(e.g., Bluetooth™ and WLAN circuitry). The client station 106 mayfurther include one or more smart cards 310 that incorporate SIM(Subscriber Identity Module) functionality, such as one or more UICC(s)(Universal Integrated Circuit Card(s)) cards 345. The cellularcommunication circuitry 330 may couple to one or more antennas, such asantennas 335 and 336 as shown. The short to medium range wirelesscommunication circuitry 329 may also couple to one or more antennas,such as antennas 337 and 338 as shown. Alternatively, the short tomedium range wireless communication circuitry 329 may couple to theantennas 335 and 336 in addition to, or instead of, coupling to theantennas 337 and 338. The short to medium range wireless communicationcircuitry 329 may include multiple receive chains and/or multipletransmit chains for receiving and/or transmitting multiple spatialstreams, such as in a multiple-input multiple output (MIMO)configuration. Some or all components of the short to medium rangewireless communication circuitry 329 and/or the cellular communicationcircuitry 330 may be used for ranging communications, e.g., using WLAN,Bluetooth, and/or cellular communications.

As shown, the SOC 300 may include processor(s) 302, which may executeprogram instructions for the client station 106 and display circuitry304, which may perform graphics processing and provide display signalsto the display 360. The SOC 300 may also include motion sensingcircuitry 370 which may detect motion of the client station 106, forexample using a gyroscope, accelerometer, and/or any of various othermotion sensing components. The processor(s) 302 may also be coupled tomemory management unit (MMU) 340, which may be configured to receiveaddresses from the processor(s) 302 and translate those addresses tolocations in memory (e.g., memory 306, read only memory (ROM) 350, NANDflash memory 310) and/or to other circuits or devices, such as thedisplay circuitry 304, cellular communication circuitry 330, short rangewireless communication circuitry 329, connector interface (I/F) 320,and/or display 360. The MMU 340 may be configured to perform memoryprotection and page table translation or set up. In some embodiments,the MMU 340 may be included as a portion of the processor(s) 302.

As noted above, the client station 106 may be configured to communicatewirelessly directly with one or more neighboring client stations. Theclient station 106 may be configured to communicate according to a WLANRAT for communication in a WLAN network, such as that shown in FIG. 1Cor for ranging as shown in FIG. 1A. Further, in some embodiments, asfurther described below, client station 106 may be configured to performerror recovery for a ranging procedure. Thus, in some embodiments, theclient station 106 may be configured to negotiate one or more rangingparameters that may include at least a set of secure training sequences.In addition, the client station 106 may receive a first ranging framethat may include a first dialog token. A first secure training sequenceof the set of secure training sequences may appended to the firstranging frame. The client station 106 may determine that the firstranging frame can be decoded based on the first dialog token but notcorrelated based on the first secure training sequence. The clientstation 106 may transmit a first acknowledgment. A second securetraining sequence of the set of secure training sequences may beappended to the first acknowledgment and the second secure trainingsequence may be associated with a prior dialog token. The client station106 may receive a second ranging frame that may include a second dialogtoken. A third secure training sequence of the set of secure trainingsequences may be appended to the second ranging frame. The clientstation 106 may determine that the second ranging frame can be decodedbased on the third dialog token and correlated based on the third securetraining sequence.

In some embodiments, a client station 106 may negotiate one or moreranging parameters that may include at least a set of secure trainingsequences and may transmit a first ranging frame that may include afirst dialog token. A first secure training sequence of the set ofsecure training sequences may be appended to the first ranging frame.The client station 106 may transmit a second ranging frame that mayinclude a second dialog token. A second secure training sequence of theset of secure training sequences may be appended to the second rangingframe. The client station 106 may receive a first acknowledgment. Athird secure training sequence of the set of secure training sequencesmay be appended to the first acknowledgment and the third securetraining sequence may be associated with the first dialog token. Theclient station 106 may determine that the first acknowledgment can bedecoded but cannot be correlated based on the third secure trainingsequence and may transmit a third ranging frame that may include a thirddialog token. A fourth secure training sequence of the set of securetraining sequences may be appended to the third ranging frame.

As described herein, the client station 106 may include hardware andsoftware components for implementing the features described herein. Forexample, the processor 302 of the client station 106 may be configuredto implement part or all of the features described herein, e.g., byexecuting program instructions stored on a memory medium (e.g., anon-transitory computer-readable memory medium). Alternatively (or inaddition), processor 302 may be configured as a programmable hardwareelement, such as an FPGA (Field Programmable Gate Array), or as an ASIC(Application Specific Integrated Circuit). Alternatively (or inaddition) the processor 302 of the UE 106, in conjunction with one ormore of the other components 300, 304, 306, 310, 320, 330, 335, 340,345, 350, 360 may be configured to implement part or all of the featuresdescribed herein.

In addition, as described herein, processor 302 may include one or moreprocessing elements. Thus, processor 302 may include one or moreintegrated circuits (ICs) that are configured to perform the functionsof processor 302. In addition, each integrated circuit may includecircuitry (e.g., first circuitry, second circuitry, etc.) configured toperform the functions of processor(s) 204.

Further, as described herein, cellular communication circuitry 330 andshort-range wireless communication circuitry 329 may each include one ormore processing elements. In other words, one or more processingelements may be included in cellular communication circuitry 330 andalso in short range wireless communication circuitry 329. Thus, each ofcellular communication circuitry 330 and short-range wirelesscommunication circuitry 329 may include one or more integrated circuits(ICs) that are configured to perform the functions of cellularcommunication circuitry 330 and short-range wireless communicationcircuitry 329, respectively. In addition, each integrated circuit mayinclude circuitry (e.g., first circuitry, second circuitry, etc.)configured to perform the functions of cellular communication circuitry330 and short-range wireless communication circuitry 329.

FIG. 3B—Wireless Node Block Diagram

FIG. 3B illustrates one possible block diagram of a wireless node 107,which may be one possible exemplary implementation of the device 100illustrated in FIG. 1B. As shown, the wireless node 107 may include asystem on chip (SOC) 300, which may include portions for variouspurposes. For example, as shown, the SOC 300 may include processor(s)302 which may execute program instructions for the wireless node 107,and display circuitry 304 which may perform graphics processing andprovide display signals to the display 360. The SOC 300 may also includemotion sensing circuitry 370 which may detect motion of the wirelessnode 107, for example using a gyroscope, accelerometer, and/or any ofvarious other motion sensing components. The processor(s) 302 may alsobe coupled to memory management unit (MMU) 340, which may be configuredto receive addresses from the processor(s) 302 and translate thoseaddresses to locations in memory (e.g., memory 306, read only memory(ROM) 350, flash memory 310). The MMU 340 may be configured to performmemory protection and page table translation or set up. In someembodiments, the MMU 340 may be included as a portion of theprocessor(s) 302.

As shown, the SOC 300 may be coupled to various other circuits of thewireless node 107. For example, the wireless node 107 may includevarious types of memory (e.g., including NAND flash 310), a connectorinterface 320 (e.g., for coupling to a computer system, dock, chargingstation, etc.), the display 360, and wireless communication circuitry330 (e.g., for LTE, LTE-A, CDMA2000, Bluetooth, Wi-Fi, NFC, GPS, etc.).

The wireless node 107 may include at least one antenna, and in someembodiments, multiple antennas 335 and 336, for performing wirelesscommunication with base stations and/or other devices. For example, thewireless node 107 may use antennas 33 and 336 to perform the wirelesscommunication. As noted above, the wireless node 107 may in someembodiments be configured to communicate wirelessly using a plurality ofwireless communication standards or radio access technologies (RATs).

The wireless communication circuitry 331 may include Wi-Fi Logic 332, aCellular Modem 334, and Bluetooth Logic 339. The Wi-Fi Logic 332 is forenabling the wireless node 107 to perform Wi-Fi communications, e.g., onan 802.11 network. The Bluetooth Logic 339 is for enabling the wirelessnode 107 to perform Bluetooth communications. The cellular modem 334 maybe capable of performing cellular communication according to one or morecellular communication technologies. Some or all components of thewireless communication circuitry 331 may be used for rangingcommunications, e.g., using WLAN, Bluetooth, and/or cellularcommunications.

As described herein, wireless node 107 may include hardware and softwarecomponents for implementing embodiments of this disclosure. For example,one or more components of the wireless communication circuitry 331(e.g., Wi-Fi Logic 332) of the wireless node 107 may be configured toimplement part or all of the methods described herein, e.g., by aprocessor executing program instructions stored on a memory medium(e.g., a non-transitory computer-readable memory medium), a processorconfigured as an FPGA (Field Programmable Gate Array), and/or usingdedicated hardware components, which may include an ASIC (ApplicationSpecific Integrated Circuit). For example, in some embodiments, asfurther described below, wireless node 107 may be configured to performerror recovery for a ranging procedure. Thus, in some embodiments, thewireless node 107 may be configured to negotiate one or more rangingparameters that may include at least a set of secure training sequences.In addition, the wireless node 107 may receive a first ranging framethat may include a first dialog token. A first secure training sequenceof the set of secure training sequences may appended to the firstranging frame. The wireless node 107 may determine that the firstranging frame can be decoded based on the first dialog token but notcorrelated based on the first secure training sequence. The wirelessnode 107 may transmit a first acknowledgment. A second secure trainingsequence of the set of secure training sequences may be appended to thefirst acknowledgment and the second secure training sequence may beassociated with a prior dialog token. The wireless node 107 may receivea second ranging frame that may include a second dialog token. A thirdsecure training sequence of the set of secure training sequences may beappended to the second ranging frame. The wireless node 107 maydetermine that the second ranging frame can be decoded based on thethird dialog token and correlated based on the third secure trainingsequence.

In some embodiments, a wireless node 107 may negotiate one or moreranging parameters that may include at least a set of secure trainingsequences and may transmit a first ranging frame that may include afirst dialog token. A first secure training sequence of the set ofsecure training sequences may be appended to the first ranging frame.The wireless node 107 may transmit a second ranging frame that mayinclude a second dialog token. A second secure training sequence of theset of secure training sequences may be appended to the second rangingframe. The wireless node 107 may receive a first acknowledgment. A thirdsecure training sequence of the set of secure training sequences may beappended to the first acknowledgment and the third secure trainingsequence may be associated with the first dialog token. The wirelessnode 107 may determine that the first acknowledgment can be decoded butcannot be correlated based on the third secure training sequence and maytransmit a third ranging frame that may include a third dialog token. Afourth secure training sequence of the set of secure training sequencesmay be appended to the third ranging frame.

Wireless Ranging

In some implementations, two wireless devices may engage in a rangingoperation so that at least one of the wireless devices will be able todetermine or estimate the range (e.g., distance) between the twodevices, e.g., by measuring an amount of time that it takes to sendmessages between the devices. For example, the Fine Timing Measurement(FTM) protocol specified in 802.11-2016 may provide a time-of-flightbased mechanism to perform ranging between two 802.11/Wi-Fi devices. InFTM, range may be determined as a function of several time instances(t1, t2, t3 and t4), where t1, t2, t3, and t4 correspond to the time ofdeparture and time of arrival of measurement frames sent in bothdirections (e.g., uplink and downlink) between the two devices (e.g.,the two STAs). Standards under development (e.g., 802.11az) may aim toimprove and/or optimize the ranging protocols for a variety of usecases, including ranging using the VHTz mode, ranging using the HEzmode, and/or ranging in the 60 GHz band, among others.

In some general ranging implementations, for example, as illustrated byFIG. 4A, two round trip equations may be used to solve two equations todetermine a range between devices. As shown, after a negotiation (e.g.,to determine a number of ranging measurement rounds and/or otherparameters associated with a ranging procedure), a responding device(rSTA) may transmit a ranging message 402 to an initiating device (iSTA)at time t1_1. Note that the initiating device (or station) may beconsidered as the device that initiated the negotiation of the rangingprocedure. The ranging message 402 may be a Fine Timing Measurement(FTM) frame that includes one or more time of departure (ToD) and timeof arrival (ToA) timestamps captured during a prior measurement round.In addition, the FTM frame may include a dialog token that may beincremented with each measurement round. In addition, each FTM frame, aswell as each acknowledgment frame, may include (or have appended) aknown preamble (e.g., training sequence). The initiating device mayreceive the ranging message 402 at time t2_1. After processing theranging message 402, the initiating device may transmit, at time t3_1, aresponse message 404 (e.g., an acknowledgment of ranging message 402).The responding device may receive the response message 404 at time t4_1.The responding device may process the response message 404 and maytransmit a ranging message 406 at time t1_2. The ranging message 406 mayinclude data (or timestamps) associated with times t1_1 and t4_1. Theinitiating device may receive the ranging message 406 at time t2_2. Atthis point, the initiating device may calculate a round trip time (RTT)based on t1_1, t2_1, t3_1, and t4_1. In addition, the initiating devicemay send a response message 408 to confirm receipt of ranging message406. The responding device may receive the response message 408 at timet4_2. The process may be repeated for the remaining measurement rounds.In some implementations, if a transmission error occurs (e.g., an iSTAfails to receive a ranging message or an rSTA fails to receive aresponse message), a retransmission (e.g., of a ranging message) of thefailed message may occur. In some implementations, the retransmissionmay be subject to the retransmission including identical ranging data asthe missed transmission, the retransmission updating an included dialogtoken if the failed message included a non-zero dialog token, and theretransmission updating a sequence number in a medium access control(MAC) header.

In some implementations, an initiating device may negotiate a securedranging procedure with a responding device. In a secured rangingprocedure, the initiating and responding devices negotiate randomtraining sequences to exchange during the secured ranging procedureinstead of the known training sequences included in an un-securedranging procedure, e.g., as discussed above. For example, FIG. 4Billustrates a secured ranging procedure according to someimplementations. As shown, an initiating device (iSTA) may transmit aninitial FTM request 420 to a responding device (rSTA). The initial FTMrequest 420 may include FTM parameters as well as security parametersassociated with a specific protocol such as directional multi gigabit(DMG) and/or enhanced DMG (EDMG). Upon receipt of FTM request 420, therSTA may derive random (or pseudo-random) numbers r_Nonce and i_Noncefrom an FTM pairwise transient key (PTK) and a hardware random numbergenerator (RNG). Subsequently, the rSTA may transmit an acknowledgementmessage 422 to the iSTA. Then, at time t1_1, the rSTA may transmit FTMmessage 424 to the iSTA. The FTM message 424 may include a dialog tokenindicating a measurement round and may have an appended random trainingsequence associated with the dialog token. The iSTA may receive the FTMmessage 424 at time t2_1 and may decode the FTM message 424 to obtainthe dialog token. Once the dialog token has been obtained, the iSTA mayconfirm (or correlate/cross correlate) the random training sequence. Atime t3_1, the iSTA may transmit an acknowledge (ACK) message 426 andmay append a random training sequence. The rSTA may receive the ACKmessage 426 at time t4_1. Subsequently, the rSTA may initiate a secondround of measurements by transmitting FTM message 428 at time t1_2. FTMmessage 428 may include a dialog token indicating the measurement roundand timestamps t1_1 and t4_1. In addition, the FTM message 428 may havean appended random training sequence associated with the dialog token.The iSTA may receive the FTM message 428 at time t2_2 and may decode theFTM message 428 to obtain the dialog token. Once the dialog token hasbeen obtained, the iSTA may confirm (or correlate/cross correlate) therandom training sequence. The iSTA may then calculate an RTT for thefirst measurement round based on the timestamps t1_1, t2_1, t3_1, andt4_1. Additionally, the iSTA may transmit ACK 430 at time t3_2. The ACK430 may have a random training sequence appended by the iSTA. ACK 430may be received by the rSTA at time t4_2. The process may be repeateduntil the negotiated number of measurement rounds have been completed.

However, unlike an unsecured ranging procedure, if an error occursduring the secured ranging procedure (e.g., as illustrated by FIG. 4C(failed FTM message 434) and 4D (failed ACK 436)), the rSTA/iSTA cannotsimply retransmit the failed message (or frame) since the transmittingdevice cannot reuse the training sequence appended to the failedmessage. For example, a rogue (or attacking device) may jam an initialFTM transmission such that a receiving device cannot decode the FTMtransmission. Then, if the transmitting device attempts to retransmitthe initial FTM transmission with the same appended training sequence,the rogue device may be able to decode the retransmitted frame and/orperform a reply attack. Thus, upon retransmission, a new trainingsequence is required. However, this leads to the devices becoming out ofsync and further may lead to failure of the ranging procedure.

FTM Secured Ranging Error Recovery

In some embodiments, an error recovery scheme for errors occurringduring a secured Fine Timing Measurement (FTM) procedure may include oneor more rules. In some embodiments, the one or more rules may include:

(1) If an FTM frame retransmission is successful, an initiating stationmay derive (or calculate) a round trip time (RTT) based on received timeof departure (ToD) (e.g., t1 value) and time of arrival (ToA) (e.g., t4value) values included in the retransmitted FTM frame and ToD (e.g., t3value) and ToA (e.g., t2 value) values estimated locally in a prior (orpreceding) fine timing measurement;

(2) During the FTM frame retransmission, a local ToA value estimated bythe initiating station may not be used for an RTT calculation in asubsequent fine time measurement;

(3) During the FTM frame retransmission, the received ToD (e.g.,estimated by the responding station) may not be included in a subsequentFTM frame;

(4) A fine timing measurement immediately after an FTM frameretransmission may not be used by an initiating station for an RTTcalculation; and

(5) A successful FTM frame retransmission may only be counted towards atotal number of measurement rounds (e.g., a negotiated FTMs per burstvalue).

In some embodiments, the local ToA value may not be used for the RTTcalculation in a subsequent fine timing measurement because the localToA may have been estimated by correlating two unmatched secure randomtraining sequences as a result of the FTM frame retransmission.Similarly, in some embodiments, the received ToD may not be included inthe subsequent FTM frame because the received ToD may have beenestimated by correlating two unmatched secure random training sequencesas a result of the FTM frame retransmission. Further, in someembodiments, the fine timing measurement immediately after an FTM frameretransmission may not be used by an initiating station for an RTTcalculation because both the local ToA and received ToD may have beenestimated by correlating two unmatched secure random training sequencesas a result of the FTM frame retransmission.

In some embodiments, FTM retransmissions may not be allowed during anFTM based secure ranging procedure. In such embodiments, to recover froma transmission error (e.g., resulting in a responding station notreceiving an acknowledgement of an FTM frame transmission), a respondingstation may transmit a new FTM frame with an updated dialog token, notimestamp data, and a new secure random training sequence associatedwith the updated dialog token.

In some embodiments, a dialog token may be associated with a set ofindependent random sequences (RS) which may constitute a secure randomtraining sequence (STS). For example, a dialog token, n, may be denotedas DT_(n), and DT_(n) may equal (or be defined as) the set of RSs, e.g.,DT_(n)={RS_(n,1), RS_(n,2), RS_(n,3), . . . RS_(n,M−1), RS_(n,M)} whereM is a total number of independent sequences per STS used. In someembodiments, at least N×M independent random sequences may be requiredfor an FTM measurement procedure, where N is a total number of FTMmeasurements to be successfully performed during the FTM measurementprocedure. In some embodiments, to compensate for possible FTM frameretransmissions, N may be increased to a value P, and P×M independentrandom sequences may be generated to further ensure completion of an FTMmeasurement procedure without exhaustion of the random sequences. Notethat in some embodiments, if a number of random sequences used isapproaching P (e.g., within a specified threshold or percentage of Pand/or when a threshold number or percentage of the random sequenceshave been used), an FTM measurement procedure may be aborted and a newFTM procedure (or session) may need to be negotiated (or re-negotiated).In some embodiments, one or both of the initiating device and respondingdevice may confirm (or detect) whether an STS used to correlate receivedsignals is correct. In some embodiments, confirmation (or detection)methods may include any or all of:

(1) A comparison of channel impulse responses obtained from multiplereceived signals (e.g., FTM frames for an initiating station,acknowledgment frames for a responding station);

(2) A check of channel tap delay of a channel impulse response; and/or

(3) A check of whether a dialog token matches an STS.

In some embodiments, one or both of the initiating station andresponding station may track a time within which receipt of a frame isexpected. For example, FIG. 5A illustrates an example of a timeline andframe exchange between an initiating station and a responding station,according to some embodiments. As shown, a responding station (e.g., 506r) may transmit a request to send (RTS) to an initiating station (e.g.,506 i) and start a network allocation vector (NAV) time reserving themedium over a path direction for an expected time period of the FTMprocedure. Upon reception of the RTS and after a short interframe space(SIFS), the initiating station may transmit a clear to send (CTS) to theresponding station and start a network allocation vector (NAV) timereserving the medium over a path direction for an expected time periodof the FTM procedure. Note that the RTS may be sent after a negotiationin which the initiating station may have initiated a ranging procedure(e.g., via transmission of an FTM request). Note further that both theinitiating station and/or responding station may be a device such asdevices 106, 107, and/or 112 described above. In addition, in someembodiments, the RTS and/or the CTS frames may be used to ensure mediumaccess (e.g., during the NAV) and allow for more precise tracking ofarrival times (e.g., time in which receipt of a frame is expected). Insome embodiments, RTS/CTS frames may be used to make the expected timeperiod for arrival deterministic which may lead to quicker recovery(e.g., fewer transmissions prior to receiving data useable to calculatean RTT). Note that in some embodiments, if RTS/CTS frames are not used,accuracy of tracking expecting time of arrival may be reduced due tomedium contention/congestion. In some embodiments, the FTM request mayinclude FTM parameters (e.g., priority and/or number of FTMs per burst)as well as security parameters associated with a specific protocol. Theresponding station may receive the FTM request and respond withtransmission of an acknowledgment that may indicate that the FTM requesthas been received by the responding station. Once the medium has beenreserved, e.g., after a negotiated or predefined time period 505, theresponding station may transmit a first FTM frame (e.g., FTM_i) at timet1_1. The initiating station may receive the first FTM frame at t2_1 andmay transmit an acknowledgment (e.g., ACK) after a SIFS at time t3_1. Asshown, the responding station may track expected time of arrival of theacknowledgement. In other words, the responding station may expect toreceive the acknowledgement within the time period 510. In someembodiments, if an expected frame is not received within an expectedtime period, a receiving station may use an STS associated with a nextdialog token to correlate a next received frame. For example, if aninitiating station does not receive an expected FTM frame within aspecified time period after transmitting an acknowledgment frame, theinitiating station may switch to using an STS associated with a nextdialog token in its subsequent reception of an FTM frame. In such acase, a responding station (which would not have received anacknowledgment frame for the FTM frame), may retransmit the FTM framewith the STS associated with the next dialog token.

As shown, the acknowledgement frame may be received at time t4_1 (e.g.,within the expected timeframe 510) and the responding station mayinitiate another measurement round via transmission of a second FTMframe (e.g., FTM_1) at time t1_2. The initiating station may receive thesecond FTM frame at time t1_2 and transmit an acknowledgment at timet3_2. The acknowledgment may be received by the responding station attime t4_2, which may be within the expected timeframe for receipt of theacknowledgement. In some embodiments, one or both of the initiatingstation and responding station may use additional correlators to furtherexpedite error recovery. For example, in addition to tracking expectedarrival time, the stations may implement two correlators that use STSscorresponding to a current and next dialog token inconfirming/correlating incoming STS which may maximize chances ofobtaining a correct estimate of time-of-arrival of the incoming STS.

FIGS. 5B-5C illustrate various examples of error recovery for an FTMbased secure ranging procedure, according to some embodiments. Thesignaling shown in FIGS. 5B-5C may be used in conjunction with any ofthe systems or devices shown in the above Figures, among other devices.In various embodiments, some of the signaling shown may be performedconcurrently, in a different order than shown, or may be omitted.Additional signaling may also be performed as desired.

Turning to FIG. 5B, FIG. 5B illustrates an example of recovery from amissed FTM frame transmission, according to some embodiments. As shown,an initiating station (e.g., 506 i), may initiate a ranging procedurevia transmission of an FTM request 520. The initiating station may be adevice such as devices 106, 107, and/or 112 described above. In someembodiments, the FTM request 520 may include FTM parameters (e.g.,priority and/or number of FTMs per burst) as well as security parametersassociated with a specific protocol. A responding station (e.g., 506 r)may receive the FTM request 520 and respond with transmission of anacknowledgment (ACK) frame 522. The responding station may be a devicesuch as devices 106, 107, and/or 112 described above. The ACK frame 522may indicate that the FTM request 520 has been received by the rSTA 506r.

At time t1_1, device 506 r may transmit an FTM frame 524. The FTM frame524 may include one or more null timestamps, FTM parameters, protocolspecific parameters, and a first dialog token (DT_1) associated with afirst measurement round. In addition, a secure random training sequence(STS_r1) associated with DT_1 may be appended to FTM frame 524. Device506 i may be expecting to receive the FTM frame 524 with DT_1 andappended STS_r1. However, as shown, reception of FTM frame 524 may fail.Thus, in response to not receiving an ACK frame for FTM frame 524,device 506 r may retransmit FTM frame 524 as FTM frame 540 at time t1_2.FTM frame 540 may include one or more null timestamps, FTM parameters,protocol specific parameters and a second dialog token (DT_2) associatedwith a second measurement round. In addition, a secure random trainingsequence (STS_r2) associated with DT_2 may be appended to frame 540.However, device 506 i may still expect an FTM frame with DT_1 andSTS_r1. Thus, correlation of FTM frame 540 may fail, however, device 506i may decode the FTM frame 540 with dialog token DT_2. Note that sincecorrelation failed, device 506 i may not record a timestamp value (e.g.,t2_2) for receipt of FTM frame 540. Further, since device 506 isuccessfully decoded FTM frame 540, an ACK frame 542 may be transmittedto device 506 r with an appended secure random training sequence STS_i1.Note that since correlation of FTM frame 540 failed, device 506 i maynot record a timestamp value (e.g., t3_2) associate with transmission ofACK frame 542.

Upon receipt of the ACK frame 542, device 506 r may decode the ACK frame542, however, correlation may fail as device 506 r may be expecting asecure random training sequence STS_i2 associated with DT_2. Note thatsince correlation failed, device 506 r may not record a timestamp value(e.g., t4_2) associated with receipt of ACK frame 542.

At this point, devices 506 i and 506 r may both be considered recoveredfrom the error of non-receipt of FTM frame 524. Thus, at time t1_3,device 506 r may transmit FTM frame 544 which may include one or morenull timestamps, FTM parameters, protocol specific parameters and athird dialog token (DT_3) associated with a third measurement round. Inaddition, a secure random training sequence (STS_r3) associated withDT_3 may be appended to FTM frame 544.

Further, at time t2_3, device 506 i may receive FTM frame 544 and maysuccessfully decode and correlate FTM frame 544 (e.g., since device 506i is expecting secure random training sequence STS_r3). At time t3_3,device 506 i may transmit ACK frame 546 with an appended secure randomtraining sequence STS_i3 associated with DT_3. At time t4_3, device 506r may receive ACK frame 546 and may successfully decode and correlateACK frame 546 (e.g., since device 506 r is expecting secure randomtraining sequence STS_i3).

At time t1_4, device 506 r may transmit FTM frame 548 which may includetimestamps associated with times T1_3 and t4_3, FTM parameters, protocolspecific parameters and a fourth dialog token (DT_4) associated with afourth measurement round. In addition, a secure random training sequence(STS_r4) associated with DT_4 may be appended to FTM frame 548.

Further, at time t2_4, device 506 i may receive FTM frame 548 and maysuccessfully decode and correlate FTM frame 548 (e.g., since device 506i is expecting secure random training sequence STS_r4). At time t3_4,device 506 i may transmit ACK frame 550 with an appended secure randomtraining sequence STS_i4 associated with DT_4. In addition, device 506 imay calculate a round trip time (RRT) associated with timestamps t1_3,t2_3, t3_3, and t4_3. At time t4_4, device 506 r may receive ACK frame550 and may successfully decode ACK frame 550 and correlate STS (e.g.,since device 506 r is expecting secure random training sequence STS_i4).The signaling may then be repeated until a negotiated number of FTMs perburst has been completed.

FIG. 5C illustrates an example of recovery from a missed ACK frametransmission, according to some embodiments. As shown, an initiatingstation (e.g., 506 i), may initiate a ranging procedure via transmissionof an FTM request 520. The initiating station may be a device such asdevices 106, 107, and/or 112 described above. In some embodiments, theFTM request 520 may include FTM parameters (e.g., priority and/or numberof FTMs per burst) as well as security parameters associated with aspecific protocol. A responding station (e.g., 506 r) may receive theFTM request 520 and respond with transmission of an acknowledgment (ACK)frame 522. The responding station may be a device such as devices 106,107, and/or 112 described above. The ACK frame 522 may indicate that theFTM request 520 has been received by the rSTA 506 r.

At time t1_1, device 506 r may transmit an FTM frame 524. The FTM frame524 may include one or more null timestamps, FTM parameters, protocolspecific parameters and a first dialog token (DT_1) associated with afirst measurement round. In addition, a secure random training sequence(STS_r1) associated with DT_1 may be appended to FTM frame 524. Device506 i may be expecting to receive the FTM frame 524 with DT_1 and STS_r1and may receive the FTM frame 524 at time t2_1 and successfullycorrelate and decode FTM frame 542. However, as shown, ACK frame 526 maynot be received by device 506 r. Thus, in response to not receiving anACK frame for FTM frame 524, device 506 r may retransmit FTM frame 524as FTM frame 528 at time t1_2. FTM frame 528 may include one or morenull timestamps, FTM parameters, protocol specific parameters and asecond dialog token (DT_2) associated with a second measurement round.In addition, a secure random training sequence (STS_r2) associated withDT_2 may be appended to FTM frame 528. Device 506 i may be expecting anFTM frame with DT_2 and STS_r2; thus, correlation of FTM frame 528 maybe successful and device 506 i may record time of receipt of FTM frame528 at t2_2. ACK frame 530 may be transmitted to device 506 r at timet3_2 with an appended secure random training sequence STS_i2. At timet4_2, device 506 r may receive and successfully decode ACK frame 530(e.g., since device 506 r is expecting training sequence STS_i2).

At this point, devices 506 i and 506 r may both be considered recoveredfrom the error of non-receipt of ACK frame 526. Thus, at time t1_3,device 506 r may transmit FTM frame 532 which may include one or moretimestamps associated times t1_2 and t4_2, FTM parameters, protocolspecific parameters and a third dialog token (DT_3) associated with athird measurement round. In addition, a secure random training sequence(STS_r3) associated with DT_3 may be appended to FTM frame 532.

Further, at time t2_3, device 506 i may receive FTM frame 532 and maysuccessfully decode and correlate FTM frame 532 (e.g., since device 506i is expecting secure random training sequence STS_r3). In addition,device 506 i may calculate a round trip time (RRT) associated withtimestamps t1_2, t2_2, t3_2, and t4_2. At time t3_3, device 506 i maytransmit ACK frame 534 with an appended secure random training sequenceSTS_i3 associated with DT_3. At time t4_3, device 506 r may receive ACKframe 534 and may successfully decode and correlate ACK frame 546 (e.g.,since device 506 r is expecting secure random training sequence STS_i3).The signaling may then be repeated until a negotiated number of FTMs perburst has been completed.

FIG. 6 illustrates a block diagram of an example of a method for errorrecovery for an FTM based secure ranging procedure, according to someembodiments. The method shown in FIG. 6 may be used in conjunction withany of the systems or devices shown in the above Figures, among otherdevices. In various embodiments, some of the method elements shown maybe performed concurrently, in a different order than shown, or may beomitted. Additional method elements may also be performed as desired. Asshown, this method may operate as follows.

At 602, ranging parameters for a secure ranging procedure may benegotiated. In some embodiments, the negotiation may be between aninitiating station and a responding station. In some embodiments, eitheror both of the initiating station and/or responding station may be adevice such as devices 106, 107, and/or 112 described above. In someembodiments, the parameters may include at least a set of securetraining sequences. In some embodiments, negotiating the rangingparameters may include determining a number of measurement rounds,wherein each measurement round corresponds to a calculation of a roundtrip time (RTT). In some embodiments, each secure training sequence ofthe set of secure training sequences may be specified by a set ofindependent random sequences.

At 604, a first ranging frame may be received. The first ranging framemay include a first dialog token. In addition, a first secure trainingsequence of the set of secure training sequences may be appended to thefirst ranging frame. In some embodiments, the first ranging frame mayinclude null timestamps and one or more parameters associated with aranging protocol. In some embodiments, the first ranging frame may be aFine Timing Measurement (FTM) frame.

At 606, it may be determined that the first ranging frame can be decodedbut not correlated. In some embodiments, decoding the first rangingframe may be based, at least in part, on the first dialog token. In someembodiments, correlating the first ranging frame may be based, at leastin part, on the first secure training sequence. In some embodiments, thefirst ranging frame may not be correlated based, at least in part, onthe first secure training sequence not matching an expected securetraining sequence. For example, the first secure training sequence maybe compared to the expected secure training sequence from the set ofsecure training sequences. Based on the comparison, it may be determinedthat the expected secure training sequence is not associated with thefirst dialog token.

At 608, a first acknowledgment of the first ranging frame may betransmitted. A second secure training sequence of the set of securetraining sequences may be appended to the first acknowledgement. Inaddition, the second secure training sequence may be associated with aprior dialog token (e.g., a dialog token received prior to the firstdialog token, for example, as part of a prior measurement round).

At 610, a second ranging frame may be received. The second ranging framemay include a second dialog token. In addition, a third secure trainingsequence of the set of secure training sequences may be appended to thesecond ranging frame. In some embodiments, the second ranging frame mayinclude null timestamps and one or more parameters associated with aranging protocol. In some embodiments, the second ranging frame may be aFine Timing Measurement (FTM) frame.

At 612, it may be determined that the second ranging frame can bedecoded and correlated. In some embodiments, decoding the second rangingframe may be based, at least in part, on the second dialog token. Insome embodiments, correlating the second ranging frame may be based, atleast in part, on the third secure training sequence. In someembodiments, the second ranging frame may be correlated based, at leastin part, on the third secure training sequence matching an expectedsecure training sequence.

In some embodiments, a second acknowledgment (e.g., of the secondranging frame) may be transmitted. Further, a third ranging frame may bereceived. In some embodiments, the third ranging frame may includetimestamps associated with transmission of the second ranging frame andreception of the second acknowledgement. In some embodiments, a roundtrip time may be calculated based on the received timestamps associatedwith transmission of the second ranging frame and reception of thesecond acknowledgement and local timestamps associated with reception ofthe second ranging frame and transmission of the second acknowledgement.

In some embodiments, the first and second ranging frames may eachinclude null timestamps and one or more parameters associated with aranging protocol. In some embodiments, timestamps associated withreceipt of the first ranging frame and transmission of the firstacknowledgment may not be used to calculate a round trip time (RTT). Insome embodiments, correlating a secure training sequence may includeany, any combination of (e.g., one or more of), and/or all of comparingchannel impulse responses obtained from different received rangingframes, determining a channel tap delay of a channel impulse response,and/or determining a dialog token associated with the secure trainingsequence was received.

FIG. 7 illustrates a block diagram of another example of a method forerror recovery for an FTM based secure ranging procedure, according tosome embodiments. The method shown in FIG. 7 may be used in conjunctionwith any of the systems or devices shown in the above Figures, amongother devices. In various embodiments, some of the method elements shownmay be performed concurrently, in a different order than shown, or maybe omitted. Additional method elements may also be performed as desired.As shown, this method may operate as follows.

At 702, ranging parameters for a secure ranging procedure may benegotiated. In some embodiments, the negotiation may be between aninitiating station and a responding station. In some embodiments, eitheror both of the initiating station and/or responding station may be adevice such as devices 106, 107, and/or 112 described above. In someembodiments, the parameters may include at least a set of securetraining sequences. In some embodiments, negotiating the rangingparameters may include determining a number of measurement rounds,wherein each measurement round corresponds to a calculation of a roundtrip time (RTT). In some embodiments, each secure training sequence ofthe set of secure training sequences may be specified by a set ofindependent random sequences.

At 704, a first ranging frame may be transmitted. The first rangingframe may include a first dialog token. In addition, a first securetraining sequence of the set of secure training sequences may beappended to the first ranging frame. In some embodiments, the firstranging frame may include null timestamps and one or more parametersassociated with a ranging protocol. In some embodiments, the firstranging frame may be a Fine Timing Measurement (FTM) frame.

At 706, a second ranging frame may be transmitted. The second rangingframe may include a second dialog token. In addition, a second securetraining sequence of the set of secure training sequences may beappended to the second ranging frame. In some embodiments, the secondranging frame may include null timestamps and one or more parametersassociated with a ranging protocol. In some embodiments, the secondranging frame may be a Fine Timing Measurement (FTM) frame.

At 708, a first acknowledgment of the second ranging frame may bereceived. A third secure training sequence of the set of secure trainingsequences may be appended to the first acknowledgement. In addition, thethird secure training sequence may be associated with the dialog token.

At 710, it may be determined that the first acknowledgement can bedecoded but not correlated. In some embodiments, decoding the firstacknowledgment may be based, at least in part, on the first dialogtoken. In some embodiments, correlating the first ranging frame may bebased, at least in part, on the third secure training sequence. In someembodiments, the first acknowledgement may not be correlated based, atleast in part, on the third secure training sequence not matching anexpected secure training sequence. For example, the third securetraining sequence may be compared to the expected secure trainingsequence from the set of secure training sequences. Based on thecomparison, it may be determined that the expected secure trainingsequence is not associated with the first dialog token.

At 712, a third ranging frame may be transmitted. The third rangingframe may include a third dialog token. In addition, a fourth securetraining sequence of the set of secure training sequences may beappended to the third ranging frame. In some embodiments, the thirdranging frame may include null timestamps and one or more parametersassociated with a ranging protocol. In some embodiments, the thirdranging frame may be a Fine Timing Measurement (FTM) frame.

In some embodiments, a second acknowledgment (e.g., of the secondranging frame) may be received. Further, a fourth ranging frame may betransmitted. In some embodiments, the fourth ranging frame may includetimestamps associated with transmission of the third ranging frame andreception of the second acknowledgement.

In some embodiments, the first and second ranging frames may eachinclude null timestamps and one or more parameters associated with aranging protocol. In some embodiments, correlating a secure trainingsequence may include any, any combination of (e.g., one or more of),and/or all of comparing channel impulse responses obtained fromdifferent received ranging frames, determining a channel tap delay of achannel impulse response, and/or determining a dialog token associatedwith the secure training sequence was received.

Embodiments of the present disclosure may be realized in any of variousforms. For example, some embodiments may be realized as acomputer-implemented method, a computer-readable memory medium, or acomputer system. Other embodiments may be realized using one or morecustom-designed hardware devices such as ASICs. Other embodiments may berealized using one or more programmable hardware elements such as FPGAs.

In some embodiments, a non-transitory computer-readable memory mediummay be configured so that it stores program instructions and/or data,where the program instructions, if executed by a computer system, causethe computer system to perform a method, e.g., any of the methodembodiments described herein, or, any combination of the methodembodiments described herein, or, any subset of any of the methodembodiments described herein, or, any combination of such subsets.

In some embodiments, a wireless device may be configured to include aprocessor (or a set of processors) and a memory medium, where the memorymedium stores program instructions, where the processor is configured toread and execute the program instructions from the memory medium, wherethe program instructions are executable to cause the wireless device toimplement any of the various method embodiments described herein (or,any combination of the method embodiments described herein, or, anysubset of any of the method embodiments described herein, or, anycombination of such subsets). The device may be realized in any ofvarious forms.

Although the embodiments above have been described in considerabledetail, numerous variations and modifications will become apparent tothose skilled in the art once the above disclosure is fully appreciated.It is intended that the following claims be interpreted to embrace allsuch variations and modifications.

What is claimed is:
 1. A wireless device, comprising: at least oneantenna; at least one radio communicatively coupled to the antenna andconfigured to perform wireless communications according to at least oneradio access technology (RAT); at least one processor communicativelycoupled to the at least one radio, wherein the wireless device isconfigured to perform voice and/or data communications; wherein the atleast one processor is configured to cause the wireless device to:negotiate one or more ranging parameters comprising at least a set ofsecure training sequences, wherein each secure training sequence of theset of secure training sequences is specified by a set of independentrandom sequences; determine that a first ranging frame received from aneighboring wireless device can be decoded based on an included firstdialog token but cannot be correlated based on an appended first securetraining sequence of the set of secure training sequences; transmit afirst acknowledgment with an appended second secure training sequence ofthe set of secure training sequences to the neighboring wireless device,wherein the second secure training sequence is associated with a priordialog token; and determine that a second ranging frame received fromthe neighboring wireless device can be decoded based on an includedsecond dialog token and can be correlated based on an appended thirdsecure training sequence of the set of secure training sequences.
 2. Thewireless device of claim 1, wherein, to determine that the first rangingframe cannot be correlated, the at least one processor is furtherconfigured to cause the wireless device to: compare the first securetraining sequence to an expected secure training sequence of the set ofsecure training sequences; and determine that the expected securetraining sequence is not associated with the first dialog token.
 3. Thewireless device of claim 1, wherein the at least one processor isfurther configured to cause the wireless device to: transmit a secondacknowledgment; and receive a third ranging frame from the neighboringwireless device, wherein the third ranging frame includes timestampsassociated with transmission of the second ranging frame and receptionof the second acknowledgement.
 4. The wireless device of claim 3,wherein the at least one processor is further configured to cause thewireless device to: calculate a round trip time based on the receivedtimestamps associated with transmission of the second ranging frame andreception of the second acknowledgement and local timestamps associatedwith reception of the second ranging frame and transmission of thesecond acknowledgement.
 5. The wireless device of claim 1, wherein thefirst and second ranging frames each include null timestamps and one ormore parameters associated with a ranging protocol.
 6. The wirelessdevice of claim 1, wherein the first ranging frame is a Fine TimingMeasurement (FTM) frame.
 7. The wireless device of claim 1, whereintimestamps associated with receipt of the first ranging frame andtransmission of the first acknowledgment are not used to calculate around trip time.
 8. The wireless device of claim 1, wherein the one ormore ranging parameters further comprise a number of measurement rounds,wherein each measurement round corresponds to a calculation of a roundtrip time RTT.
 9. The wireless device of claim 1, where, to correlate asecure training sequence, the at least one processor is furtherconfigured to cause the wireless device to perform one or more of:comparing channel impulse responses obtained from different receivedranging frames; determining a channel tap delay of a channel impulseresponse; and/or determining a dialog token associated with the securetraining sequence was received.
 10. An apparatus, comprising: a memory;and at least one processor in communication with the memory, wherein theat least one processor is configured to: determine that a first rangingframe received from a neighboring wireless device can be decoded basedon an included first dialog token but cannot be correlated based on anappended first secure training sequence of a set of secure trainingsequences, wherein the set of secure training sequences is negotiatedprior to receipt of the first ranging frame, wherein each securetraining sequence of the set of secure training sequences is specifiedby a set of independent random sequences, and wherein correlating thefirst secure training sequence includes at least one of comparingchannel impulse responses obtained from different received rangingframes, determining a channel tap delay of a channel impulse response,or determining a dialog token associated with the secure trainingsequence was received; generate instructions to cause a firstacknowledgment with an appended second secure training sequence of theset of secure training sequences to be transmitted to the neighboringwireless device, wherein the second secure training sequence isassociated with a prior dialog token; and determine that a secondranging frame received from the neighboring wireless device can bedecoded based on an included second dialog token and can be correlatedbased on an appended third secure training sequence of the set of securetraining sequences.
 11. The apparatus of claim 10, wherein, to determinethat the first ranging frame cannot be correlated, the at least oneprocessor is further configured to: compare the first secure trainingsequence to an expected secure training sequence of the set of securetraining sequences; and determine that the expected secure trainingsequence is not associated with the first dialog token.
 12. Theapparatus of claim 10, wherein the at least one processor is furtherconfigured to: generate instructions to cause a second acknowledgment tobe transmitted to the neighboring wireless device; receive a thirdranging frame from the neighboring wireless device, wherein the thirdranging frame includes timestamps associated with transmission of thesecond ranging frame and reception of the second acknowledgement; andcalculate a round trip time based on the received timestamps associatedwith transmission of the second ranging frame and reception of thesecond acknowledgement and local timestamps associated with reception ofthe second ranging frame and transmission of the second acknowledgement.13. The apparatus of claim 10, wherein the first and second rangingframes each include null timestamps and one or more parametersassociated with a ranging protocol.
 14. The apparatus of claim 10,wherein the first ranging frame is a Fine Timing Measurement (FTM)frame.
 15. The apparatus of claim 10, wherein timestamps associated withreceipt of the first ranging frame and transmission of the firstacknowledgment are not used to calculate a round trip time.
 16. Theapparatus of claim 10, wherein the one or more ranging parametersfurther comprise a number of measurement rounds, wherein eachmeasurement round corresponds to a calculation of a round trip time RTT.17. A non-transitory computer readable memory medium storing programinstructions executable by processing circuitry of a wireless device to:negotiate one or more ranging parameters comprising at least a set ofsecure training sequences; receive a first ranging frame comprising afirst dialog token, wherein a first secure training sequence of the setof secure training sequences is appended to the first ranging frame;determine that first ranging frame can be decoded based on the firstdialog token but not correlated based on the first secure trainingsequence; generate instructions to cause a first acknowledgment to betransmitted with an appended second secure training sequence of the setof secure training sequences, wherein the second secure trainingsequence is associated with a prior dialog token; receive a secondranging frame comprising a second dialog token, wherein a third securetraining sequence of the set of secure training sequences is appended tothe second ranging frame; and determine that the second ranging framecan be decoded based on the third dialog token and correlated based onthe third secure training sequence.
 18. The non-transitory computerreadable memory medium of claim 17, wherein, to determine that the firstranging frame cannot be correlated, the program instructions are furtherexecutable to: compare the first secure training sequence to an expectedsecure training sequence of the set of secure training sequences; anddetermine that the expected secure training sequence is not associatedwith the first dialog token.
 18. The non-transitory computer readablememory medium of claim 17, wherein the program instructions are furtherexecutable to: generate instructions to cause a second acknowledgment tobe transmitted to the neighboring wireless device; receive a thirdranging frame from the neighboring wireless device, wherein the thirdranging frame includes timestamps associated with transmission of thesecond ranging frame and reception of the second acknowledgement; andcalculate a round trip time based on the received timestamps associatedwith transmission of the second ranging frame and reception of thesecond acknowledgement and local timestamps associated with reception ofthe second ranging frame and transmission of the second acknowledgement.20. The non-transitory computer readable memory medium of claim 17,wherein correlating a secure training sequence comprises one or more of:comparing channel impulse responses obtained from different receivedranging frames; determining a channel tap delay of a channel impulseresponse; and/or determining a dialog token associated with the securetraining sequence was received.